1. Field of the Invention
The present invention relates to a gate valve capable of opening and closing a transfer path for transferring a workpiece, for example an integrated circuit (IC) or components therefor, from one vacuum processing chamber to another vacuum processing chamber, or for opening and closing a fluid flow path, or an exhaust flow path, for a pressurized fluid or gas or the like.
2. Description of the Related Art
Conventionally, in processing apparatuses for semiconductor wafers or liquid crystal substrates for example, insertion and withdrawal of such semiconductor wafers or liquid crystal substrates from various kinds of processing chambers is undertaken via communication passageways, wherein within such passageways, respectively, gate valves are disposed for opening and closing the communication passageways.
For example, as disclosed in Japanese Patent Document No. 2,613,171 (corresponding to U.S. Pat. Nos. 5,415,376 and 5,641,149), such a gate valve is disposed in such a way that, after a valve disk arrives at an opposing position with respect to a valve seat by direct advancing movement of a valve rod displaced under an actuating operation of a cylinder, the valve disk is pressed into contact and seated on the valve seat by an inclining movement of the valve rod, thereby closing a communication passageway formed within a valve box.
More specifically, as shown in FIGS. 27 and 28, the gate valve according to the conventional technique comprises a valve box 3 having formed therein a communication passageway 2 for insertion and withdrawal of a workpiece, a valve disk 5 for opening and closing the communication passageway 2 by means of seating the valve disk 5 onto a valve seat 4 formed within the valve box 3, and a valve rod 6 connected to the valve disk 5 and capable of making up and down movements as well as being tiltably movable.
A valve block 7 is connected to an upper portion of the valve rod 6, wherein on both side surfaces of the valve block 7 pivot axles 11 are attached which are displaced along guide grooves 10 (see FIG. 29) which are formed respectively in both side surfaces of the cylinder tubes 9 of a pair of cylinders 8a, 8b, and wherein the block 7 is disposed so as to move up and down and to be tilted under a guiding action of the guide grooves 10 which engage with the pivot axles 11. The cylinder tube 9, block 7 and pivot axles 11 are each formed respectively from a metallic material.
Stated otherwise, the block 7 is structured for making a direct advancing movement along the vertical direction in unison with a yoke 13 via a contracting spring 12 which exerts a pulling force, while under a guiding action of the guide grooves 10 which engage with the pivot axles 11, and in addition, for making a tilting movement in the direction of arrow A with the axles 11 serving as a pivot point (fulcrum) when supported by curved lower ends 10a (see FIG. 29) of the guide grooves 10 (see FIG. 28). As a result, the disk 5, with the axles 11 serving as a fulcrum, makes a tilting movement in the direction of arrow B and is seated on the valve seat 4, whereby the communication passageway 2 is airtightly closed.
Moreover, reference numeral 14 indicates a cross-sectionally diamond shaped cam plate, wherein by displacement of the cam plate 14 so as to become substantially horizontal, the block 7 is caused to undergo inclined movement in the direction of arrow A, with the lower curved parts 10a of the guide grooves 10 serving as a fulcrum.
Notwithstanding, with the gate valve according to the above-mentioned conventional technique, because the block axles are disposed for sliding displacement along guide grooves formed in both side surfaces of the cylinders, over extended periods of use, the axles are subjected to frictional wear and hence become deformed, so that a disadvantage results in that their guiding function is lessened in ability.
Further, in the gate valve according to the conventional technique, because axles must be disposed on both sides of the valve block, the number of parts increases, and in addition, a process step for machining or cutting out the guide grooves in both sides of the cylinders becomes necessary, so there is the disadvantage of increased production costs.
Furthermore, in the gate valve according to the conventional technique, as a result of the fact that the axles of the valve block which are formed of a metallic material are slidingly displaced in contact along guide grooves of the cylinder tubes which likewise are formed from a metallic material, dirt or dust and so forth tends to develop. Stated otherwise, a further disadvantage results in that, due to generation of dust caused by friction between the metallic parts, the device cannot be used in an environment which demands purity, such as a clean room or the like.
A general object of the present invention is to provide a gate valve in which, by eliminating the need for a guide means, the number parts can be decreased, and thereby production costs can be reduced.
A further main object of the present invention is to provide a gate valve capable of being suitably used in an environment demanding purity, by suppressing generation of dust, dirt and the like.
Another object of the present invention is to provide a gate valve in which there is disposed a positioning support structure for integrally maintaining a first displacement member and a second displacement member in a predetermined positional state along a displacement direction, and which is capable of maintaining the position-determined condition of the first and second displacement members, even after extended periods of use.
The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative example.